The lagoon triggerfish, (Rhinecanthus aculeatus) also known as the blackbar triggerfish, the Picassofish, and the Jamal, is a triggerfish

Triggerfish

Triggerfishes are about 40 species of often brightly colored fishes of the family Balistidae. Often marked by lines and spots, they inhabit tropical and subtropical oceans throughout the world, with the greatest species richness in the Indo-Pacific...

, up to 30 cm in length, found on reefs in the Indo-Pacific

Indo-Pacific

The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...

 region.

The Hawaiian

Hawaiian language

The Hawaiian language is a Polynesian language that takes its name from Hawaii, the largest island in the tropical North Pacific archipelago where it developed. Hawaiian, along with English, is an official language of the state of Hawaii...

 name for the fish, (ˈhumuˈhumuˈnukuˈnukuˈwaːpuˈwɐʔə), also spelled humuhumu-nukunuku-a-pua‘a or just humuhumu for short (meaning "triggerfish with a snout like a pig") shares the same name with the reef triggerfish

Reef triggerfish

The reef, rectangular, or wedge-tail triggerfish, also known by its Hawaiian name, humu­humu­nuku­nuku­āpuaa , also spelled Humuhumunukunukuapua'a or just humuhumu for short; meaning "triggerfish with a snout like a pig"), is one of several species of triggerfish...

, the state fish of Hawaii

Hawaii

Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

.

This species has been studied in a range of research contexts, from locomotion

Animal locomotion

Animal locomotion, which is the act of self-propulsion by an animal, has many manifestations, including running, swimming, jumping and flying. Animals move for a variety of reasons, such as to find food, a mate, or a suitable microhabitat, and to escape predators...

 to colour vision research.

Behavior

Lagoon triggerfish lives in the reefs and sandy areas of coral reef

Coral reef

Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...

s where it eats just about everything that comes along. They are always restlessly swimming around and can vigorously protect their territory against intruders, including divers, especially when guarding their eggs during reproduction season. Fortunately, their relative small size makes them much less dangerous than the larger titan triggerfish

Titan triggerfish

The titan triggerfish, giant triggerfish or moustache triggerfish is a large species of triggerfish found in lagoons and at reefs in most of the Indo-Pacific, though it is absent from Hawaii...

 of the same family.

Mating and reproduction

Both sexes guard territories, some maintaining a territory for eight years or longer (males holding territories for significantly longer than females). A typical male territory may overlap with one to five female territories, and their mating system is described as haremic, although not much is known about this (similar mating systems are seen in other Balistidae species). If a male or female is removed or disappears their territories are soon taken over by a new fish. They reproduce repeatedly over their lifetimes.

Pair-spawning takes place around sunrise, with the egg masses being attached to sand, coral rubble or algae. They hatch the same day around sunset. Although paternal care is normal in teleost fishes with external fertilization, it is the mothers in this species that guard and care for eggs until they hatch. The mother remains above the eggs for about 12–14 hours, fanning the eggs with her pectoral fins to improve aeration for perhaps 30% of the time. She chases away most fish that approach and remove other intruders like starfish by mouth. Maternal care is effective in preventing predation, and experimental removal of the mothers reduced survival to almost nothing suggesting this behaviour is adaptive. Unlike fathers, mothers forage less and over a smaller area near the egg mass while caring for the eggs. Since the males have multiple mates, caring for an egg mass would probably be more costly in terms of lost mating opportunities so maternal care is considered to be an evolutionarily stable strategy

Evolutionarily stable strategy

In game theory and behavioural ecology, an evolutionarily stable strategy , which is sometimes also called an evolutionary stable strategy, is a strategy which, if adopted by a population of players, cannot be invaded by any alternative strategy that is initially rare. An ESS is an equilibrium...

.

Vision

This species has one type of single cone

Cone cell

Cone cells, or cones, are photoreceptor cells in the retina of the eye that are responsible for color vision; they function best in relatively bright light, as opposed to rod cells that work better in dim light. If the retina is exposed to an intense visual stimulus, a negative afterimage will be...

 (SC), with visual pigment peaking in sensitivity at 413 nm (S), and a double cone

Double cone

Double cones , also known as twin cones in some literature, are two cone cells joined together that may also be coupled optically/electrically...

 with different visual pigments in each member peaking at 480 nm (M) and 530 nm (L) respectively. Behavioural research has provided evidence that individual members of the double cones can act as independent channels of colour information, aiding in understanding double cone function. This research suggests the species has trichromatic vision, like humans.